Adhesive mountable stack of removable layers

ABSTRACT

An eye protector includes a lens configured to protect the wearer from projectiles, and an optically clear stack attached to the lens. The stack can have one or more removable layers. The eye protector also includes an optically clear dry mount adhesive layer attaching the stack to the lens. The dry mount adhesive may be self-wetting to attach the stack to the lens so that air between the stack and the lens can be removed after the stack is attached and/or adhered to the lens, for example, by applying pressure across the surface of the stack. The refractive indices of the lens, the dry mount adhesive, and each removable layer are matched to within about 0.2.

RELATED APPLICATIONS

Not Applicable

TECHNICAL FIELD

The present disclosure generally relates to an adhesive mountable stackof lens layers. More specifically, the present disclosure relates to astack of removable lens layers configured for dry mounting to opticallyclear eye protective surfaces.

BACKGROUND

Multilayer tear off systems can be attached to eye protective surfaces,such as goggles or face shields, with pins. In this way, pins areattached outside of the primary viewing area of the eye protector, forexample, to left and right sides of the eye protector surface. To attachthe system to an eye protector, the system is wrapped tightly around theoptically clear lens of the eye protector by pulling the system over thepins. One example of a multilayer tear off system attached to pins of aneye protector is disclosed in U.S. Pat. No. 6,388,813, issued to theassignee of the instant application.

One issue that can arise with multilayer tear off systems relates to thepropensity of dirt to accumulate between the lowest layer of themultilayer tear off system and the transparent lens of the eyeprotector. This accumulation of dirt can reduce visibility through theeye protector to unacceptable or undesirable levels, thereby renderingthe multilayer tear off system sub-optimal or even detrimental.

Additionally, air disposed between the lowest layer of the system andthe lens of the eye protector can result in undesirable reflectionscaused by a mismatch in the indices of refraction between lens, thesystem, and the air disposed therebetween. These reflections can reducecontrast and light transmission and limit the amount of light that canpass through the system and eye protector, thereby reducing the wearer'svisual acuity through the eye protector.

Moreover, the pins used to secure the transparent lens of the eyeprotector can reduce the impact resistance of the eye protector. Forexample, attaching pins to the eye protector can involve drilling holesinto the eye protector so that pins can be mounted therein. These holescan create points of weakness that reduce the structural integrity ofthe eye protector, thereby limiting the ability of the eye protector toshield against projectiles or other objects. This can be particularlysignificant, for example, in military applications, where the eyeprotectors are intended to protect a wearer against high speedprojectiles or other dangerous flying debris.

Further, pins can limit the system's ability to be applied to eyeprotectors of varying shape, design, or style. For example, because pinsare positioned at a predetermined distance from one another, thecorresponding holes in the layers of the system are formed to match thispredetermined distance. But as eye protectors vary in size, shape,and/or style, different eye protectors may position the pins indifferent locations, and at different spacing intervals. Thus, a systemdesigned to match one eye protector may be unusable for a different eyeprotector.

BRIEF SUMMARY

The present disclosure describes eye protectors and methods forprotecting an eye protector without significantly reducing visual acuitytherethrough. In some embodiments, the eye protector has a centerportion defining a center of gaze of a wearer. The eye protector caninclude a lens configured to protect the wearer from projectiles. Thelens can have a lens refractive index (or index of refraction). The eyeprotector can also include an optically clear stack attached to thelens. The stack can have one or more removable layers. Each removablelayer can have a removable layer refractive index. The eye protector canalso include an optically clear dry mount adhesive layer attaching thestack to the lens. In some aspects, the dry mount adhesive layer forms acontinuous and uninterrupted adhesive surface over at least the centerportion of the eye protector. The dry mount adhesive layer can have adry mount adhesive refractive index. In at least one aspect, the drymount adhesive is self-wetting and attaches the stack to the lens sothat air between the stack and the lens can be removed after the stackis attached and/or adhered to the lens, for example, by applyingpressure across the surface of the stack. In some embodiments, the lensrefractive index, the dry mount adhesive refractive index, and eachremovable layer refractive index are matched to within about 0.2.

The present disclosure also describes an optically clear stackconfigured for affixing to a lens to form an eye protector. The eyeprotector can have a center portion defining the center of gaze of awearer. The lens can be configured to protect the wearer fromprojectiles and have a lens refractive index. The stack can include atleast one optically clear removable layer, each removable layer having aremovable layer refractive index. The stack can also include anoptically clear dry mount adhesive layer applied to a lower surface ofthe stack. The dry mount adhesive layer can be configured to attach thestack to the lens and form a continuous and uninterrupted adhesivesurface covering at least the center portion of the eye protector. Insome embodiments, the dry mount adhesive layer is self-wetting andconfigured to attach the stack to the lens so that air between the stackand the lens can be removed after the stack is attached and/or adheredto the lens, for example, by applying pressure across the surface of thestack. The dry mount adhesive layer can also have a dry mount adhesiverefractive index. In some embodiments, the lens refractive index, thedry mount adhesive refractive index, and each removable layer refractiveindex are all matched to within about 0.2.

The present disclosure also describes methods of protecting an eyeprotector without significantly reducing visual acuity through the eyeprotector. In some aspects, the eye protector can be one of the eyeprotectors described and depicted herein. For example, the eye protectorcan have a center portion defining a center of gaze of a wearer, and caninclude a lens (having a lens refractive index) configured to protectthe wearer from projectiles. In one embodiment, the method includesselecting an optically clear stack having one or more removable layers.Each of the removable layers can have a removable layer refractive indexmatched to within about 0.2 of the lens refractive index. The method canalso include removing a protective liner from a bottom surface of thelens stack to expose an optically clear dry mount adhesive layer. Themethod can also include dry mounting the stack to the lens so that theadhesive layer forms a continuous and uninterrupted adhesive layer overat least the center portion. In some embodiments, the dry mounting stepcan involve removing air between the stack and the lens, for example, byapplying pressure to the stack and smoothing or pressing out air bubblesbetween the stack and the lens. The dry mount adhesive layer can beself-wetting and have a dry mount adhesive layer refractive indexmatched to within about 0.2 of the lens refractive index and eachremovable layer refractive index.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the various embodimentsdisclosed herein will be better understood with respect to the followingdescription and drawings, in which like numbers refer to like partsthroughout, and in which:

FIG. 1 is a perspective view of a helmet with an adhesive mountablestack of removable layers adhered to a lens in accordance with at leastone embodiment of the present disclosure;

FIG. 2 is a front view of a stack in accordance with at least oneembodiment of the present disclosure;

FIG. 3 is a cross-sectional view of a stack and lens of an eye protectorin accordance with at least one embodiment of the present disclosure;

FIG. 4 is a front view of a stack with a plurality of offset tabs tofacilitate removal of an uppermost layer of the stack in accordance withat least one embodiment of the present disclosure;

FIG. 5 is a cross-sectional view of a stack with progressively steppedlayers to facilitate gripping of the uppermost layer of the stack inaccordance with at least one embodiment of the present disclosure; and

FIG. 6 is a flow chart of a method for mounting a stack to an eyeprotector in accordance with at least one embodiment of the presentdisclosure.

DETAILED DESCRIPTION

The present disclosure describes stacks mountable to an eye protectorwith an adhesive. As used throughout this specification, the term“stack” refers to a collection of one or more optically clear and/ortransparent lens(es), film(s), or other layer(s) that can be attachedand/or laminated together. As used herein, the phrase “optically clear”refers to a material having no perceptible visible distortion orscatter. An optically clear material may be transparent and/orcolorless, but in some circumstances, a material that has a hue, shade,or a tint, for example, can be considered “optically clear” consistentwith the meaning of the phrase as used herein. As used throughout thisapplication, “eye protector” refers to optically clear objects designedto provide protection to the eyes and/or face of a wearer. “Eyeprotector” can refer to eye shields, face shields, lenses, glasses,masks, goggles, visors, windows, or the like. Moreover, where aparticular eye protector is referenced (e.g., a face shield) in adescribed example, it is contemplated that other eye protectors (e.g.,goggles) can be reasonably substituted in place of the eye protectorwithout deviating from the scope of the disclosure, unless the contextof the disclosure suggests otherwise.

Embodiments of the present disclosure provide systems for maintaining orrestoring visibility through eye protectors during use while maintainingand/or maximizing visual acuity. The system may comprise a singletransparent layer or a plurality of transparent layers adhered to eachother and to a transparent lens of the eye protector. Although variousaspects disclosed herein relate to a stack having two or more removablelayers, some aspects disclosed herein may also be applicable to anembodiment having a single transparent layer. The uppermost layer of thestack can be peeled off from the next lower layer and/or the transparentlens of the eye protector to improve and/or restore visibility throughthe eye protector. The transparent lens of the eye protector, theremovable transparent layers of the stack, and the adhesive thatattaches the layers of the stack to each other and the stack to thetransparent lens may each define refractive indices that are within 0.2of each other. This can serve, for example, to limit, reduce, and/oreliminate perceptible internal reflections through the system, or tootherwise generally improve or maintain visibility through the system.Also, by adhering the lowest layer of the stack of the transparent lenswith an optically clear uninterrupted layer of adhesive, the strength,integrity, and/or durability of the transparent lens of the eyeprotector may not be diminished, which can occur, for example, when pinsare installed through the eye protector to assist with the mounting ofremovable layers. Moreover, the uninterrupted layer of adhesive canprovide a physical barrier that inhibits, thwarts, limits, reduces,and/or prevents dirt or debris from entering and accumulating betweenthe lowest layer of the stack and the transparent lens.

Some embodiments of the present disclosure describe a face shield. Theface shield can include a first transparent lens, a stack of two or moreremovable transparent layers, a dry mount adhesive layer, and one ormore optically clear stack adhesive layers. The first transparent lenscan be disposed in front of a wearer's eyes, for example, to protect thewearer's eyes from impact. The transparent lens may define a firstrefractive index (or a lens refractive index), and each layer of thestack may define a removable layer refractive index. The dry mountadhesive layer can be disposed between the first transparent lens and alowest layer of the stack so that the stack is affixed or affixable tothe first transparent lens. The dry mount adhesive layer may becontinuous and uninterrupted. In some embodiments, an outer periphery ofthe dry mount adhesive layer covers a center of gaze of a wearer. Thedry mount adhesive layer may define a dry mount adhesive refractiveindex. The stack adhesive layers may be interposed between each pair oftransparent layers of the stack so that an uppermost layer of the stackis removable from the stack. Each optically clear stack adhesive layermay define a stack adhesive refractive index. The refractive indices ofthe lens, the dry mount adhesive, each removable layer of the stack andeach adhesive layer of the stack may be within about 0.2 of each other.In some embodiments, these refractive indices are matched within an evensmaller range, for example, within 0.1, 0.05, or 0.02.

The first transparent lens can be or comprise a polycarbonate material.The dry mount adhesive layer can be or comprise an acrylic polymethylmethacrylate material or a high index silicone adhesive. The removablelayer(s) can be or comprise a polyethylene terephalate material. Thestack adhesive layers can each be or comprise an acrylic polymethylmethacrylate material or a high index silicone adhesive.

In some embodiments, the transparent lens can be a face shield of ahelmet, a lens of an eyeglass or a face shield of a goggle.

In some examples, opposed outer portions of the stack define outer edgesin a stepped format. In some aspects, the opposed outer portions areadhesive free.

Referring now to the drawings, FIG. 1 shows a system for restoringvisibility through an eye protector 12 while maintaining visual acuitytherethrough. The stack can include a single removable transparent layeror a plurality of removable transparent layers (e.g., 2-7 layers)attachable to the eye protector 12, such that the layers and peeled offone-by-one as individual layers when needed.

The stack 10 can be adhesively mountable to the eye protector 12, forexample, using a dry mount adhesive that facilitates mounting of thestack 10 to the lens 16. In some embodiments, the dry mount adhesive canbe self-wetting, and can facilitate the removal of air between the stack10 and the lens 16 after mounting. For example, because the dry mountadhesive is self-wetting, a user can remove air pockets or air bubblesthat form between the stack 10 and the lens 16 by applying pressure tothe stack 10 and smoothing or spreading pressure outwardly towards theedges of the stack 10. In this manner, a user may be able to reduce,limit, and/or eliminate perceptible air pockets between the stack andthe lens 16 after mounting.

In some embodiments, the refractive indices between the transparent lens16, the dry mount adhesive layer 18 a, the removable layers 14 a-n ofthe stack 10, and the interposed stack adhesive layers (18 b and 18 c)are all matched to within about 0.2 of each other. As a result,additional internal reflections through the eye protector 12 can besignificantly limited, reduced and/or eliminated from the wearer'sperspective.

As shown in FIG. 3, the dry mount adhesive layer can be optically clear,and may form a continuous, uninterrupted dry mount adhesive layer 18 athat allows for the stack to be dry mounted to the lens 16 of the eyeprotector 12. Dry mounting refers to an adhesive that exhibits adhesiveproperties upon removal of a protective liner without requiring liquidor heat activation. Using a layer of adhesive 18 a to mount the stack 10to the eye protector 12 creates a physical barrier that inhibits,thwarts, limits, and/or prevents dirt, dust, and/or debris fromaccumulating between the lowest layer 14 a of the stack 10 and thetransparent lens 16 of the eye protector 12. Thus, the system canmaintain visibility through the eye protector 12 even when used in dustyand dirty terrain. Also, using dry mount adhesive layer 18 a to securethe stack 10 to the eye protector 12 helps maintain the strength of thelens 16 of the eye protector 12. That is, the integrity of the lens 16need not be diminished, for example, by drilling holes in the lens tomount pins, as is sometimes done with other systems.

The layer of adhesive 18 a can be selected to help limit, reduce, and/oreliminate air in between the top surface of the lens 16 and the lowersurface of the lowest layer 14 a of the stack 10. For example, theadhesive layer 18 a can be selected as a self-wetting dry mount adhesivethat allows the stack 10 to first be applied to the lens 16, and thensmoothed or evened out, for example, by applying pressure to remove airbubbles or pockets without the use of water or other liquids. The drymount adhesive can be selected to have material properties that allowany air bubbles or air pockets forming between the stack 10 and the lens16 to be worked out relatively easily by a user. Moreover, because wateror other fluids are not necessary (e.g., because the dry mount adhesiveis self-wetting), the adhesive can dry and adhere to the lens relativelyquickly (e.g., instantly or nearly instantly), thereby inhibiting,limiting, or preventing the stack 10 from moving, sliding, ordelaminating from the lens 16.

The dry mount adhesive can also be selected to have properties thatallow the lowest layer of the stack 10 to adhere to the lens 16 with apeel strength that is greater than the peel strength between eachsuccessive layer of the stack 10. In this manner, the dry mount adhesivecan maintain a secure attachment between the stack 10 and the lens 16even when an upper layer of the stack 10 is being peeled away orotherwise removed by a user. In some embodiments, the dry mount adhesivelayer provides a peel strength sufficient to prevent the stack 10 fromsliding, moving, or delaminating from the lens in the face of high windspeeds. For example, in some aspects, the dry mount adhesive is selectedso that it can be effectively applied to prevent delamination from thelens of a windshield or face shield worn by racers that may face windspeeds in excess of 100 or 200 miles per hour. The dry mount adhesivecan also be selected to provide a peel strength that avoids adhesiontransfer; that is, the peel strength can be low enough to avoid leavingbehind an adhesive residue when the stack 10 is peeled away from thelens 16.

The dry mount adhesive can also be selected to have an optical clarity,or haze level that is less than 1.0%, and a light transmission value ofgreater than 99%. The dry mount adhesive can be selected to be capableof wetting to the surface of the lens 16 without forming bubbles betweenthe stack 10 and the lens (or in a manner that allows the bubbles to bereadily removed). The dry mount adhesive can also be selected to havehigh temperature, humidity, and UV resistance. In some embodiments, thedry mount adhesive will be selected to have non-yellowing properties.

In some embodiments, the dry mount is selected to have some or all ofthe properties described above, while also having a refractive indexthat matches the refractive index of the lens 16, the removable layers14 of the stack 10, and/or the stack adhesive layers (18 b and 18 c)laminating the layers 14 of the stack 10 together.

It has been surprisingly discovered that a polymethyl methacrylateadhesive (PMMA) can serve as a dry mount adhesive that satisfies all ofthese specifications. That is, PMMA can be used as a dry mount adhesivethat satisfies the peel strength specifications while also offering arefractive index that can be matched within 0.2 of the refractiveindices of suitable lens materials (e.g., polycarbonate), and suitableremovable layer materials (e.g., PET) and suitable stack adhesivelayers. For example, in some embodiments, the refractive index for PMMAcan be about 1.492. PMMA can also satisfy the specifications relating tooptical clarity/haze, light transmission, wetting properties, bubbleprevention/removal capabilities, temperature resistance, humidityresistance, UV resistance, and non-yellowing properties. Thus, the drymount adhesive layer can be a PMMA configured to satisfy some or all ofthese specifications, thereby facilitating dry mounting of the lowestlayer 14 a of the stack 10 to the lens 16.

The thickness of the dry mount adhesive layer 18 a can vary depending onthe use. For example, in some embodiments, the dry mount adhesive layer18 a can be between about 10 microns and 20 microns, or morespecifically between 13 microns and 17 microns, or even morespecifically, about 15 microns thick (i.e., 15 μm).

The peel strength of the dry mount adhesive can be configured tocorrelate with the peel strength of the adhesive holding the layers 14of the stack 10 together. For example, in some embodiments, the peelstrength of the dry mount adhesive may be relatively high when comparedto the peel strength of the adhesive holding the layers 14 of the stack10 together to ensure that the stack remains attached to the lens 16when the various layers 14 of the stack 10 are removed or peeled away.It should be noted, however, that using an adhesive that offers a peelstrength that is too high can present drawbacks. For example, where astack or a removable layer is mounted to a lens with a peel strengththat is greater than about 100 grams (measured at a 180° peel test at 12inch per minute rate), there can be a significant risk of adhesivetransfer. That is, where the peel strength is too high, removing thelayer or stack can cause the adhesive layer to fracture, thereby leavingbehind a residual portion of the adhesive on the lens of the eyeprotector. This adhesive residue can occlude or impair the visibilitythrough the lens, and can also make the process of mounting anotherstack or layer on the lens difficult, inefficient, and/or impossible.Thus, in some embodiments, a dry mount adhesive material is selected andconfigured so that it provides a peel strength high enough to maintainthe stack 10 attached to the lens 16 when the upper layers 14 are peeledaway, but low enough to allow the stack 10 to be removed from the lens16 without leaving behind residual adhesive.

The correlation between the peel strength of the dry mount adhesivelayer and the peel strength of the adhesive holding the layers 14 of thestack 10 together can depend upon how the stack 10 is mounted to thelens 16. For example, where the stack 10 is intended to be dry mountedto a lens 16 without the use of pins or posts applying tension to thestack, it can be useful to use a dry mount adhesive that offers a peelstrength that is about twice the peel strength necessary to remove theremovable layers 14 of the stack 10. In some embodiments, the peelstrength for each of the removable layers 14 can be between about 10grams and about 50 grams when measured using a 180° peel test at a 12inch per minute rate, with an average peel strength of about 25 grams toabout 30 grams for each layer 14. Thus, in such an embodiment, the drymount adhesive can be selected to have a peel strength of about 50 gramsto about 60 grams, i.e., about twice that of the average peel strengthof the removable layers 14.

As another example, where the stack 10 is intended to be dry mountedusing pins or posts for tension, the peel strength of the dry mountadhesive may be equal to, or even less than that of the removable layers14. Because the tension of the pins and/or posts can help maintain theposition of the stack 10 on the lens 16 when the removable layers 14 arepeeled away, the adhesive strength attaching the stack 10 to the lens 16need not be quite as high. Thus, in such an example, as long as the drymount adhesive provides sufficient tack to establish “wetting” to thelens of the eye protector without forming air bubbles, the dry mountadhesive peel strength may be sufficient. It has been surprisingly andunexpectedly discovered that a PMMA adhesive can be configured to meetthese peel strength specifications. And as noted above, PMMA can alsomeet the other specifications desirable for adhering a stack 10 to alens 16.

Other types of adhesive materials are also contemplated for the drymount adhesive layer 18 a. By way of example and not limitation, the drymount adhesive layer 18 a may be a “high index” dry mount siliconeadhesive. The high index dry mount silicone adhesive may have arefractive index between about 1.45 to 1.54. The dry mount adhesivelayer 18 a may be provided in various form factors for pre-applicationonto the lowest layer 14 a such as liquid, spray on or film. In someembodiments, the dry mount adhesive layer 18 a can facilitate the drymounting of the stack 10 to the transparent lens 16 (e.g., mountingwithout water or fluid). In some embodiments, however, the dry mountadhesive layer 18 a can (additionally and/or alternatively) be activatedwith a fluid or liquid (e.g., water), or heat.

The dry mount adhesive layer 18 a may be applied to the bottom surface20 of the lowest layer 14 a by pouring the liquid adhesive over thebottom surface and letting the liquid spread over the bottom surface 20of the lowest layer 14 a. Alternatively, the dry mount adhesive may besprayed over the bottom surface 20 of the lowest layer 14 a. As afurther alternative, the dry mount adhesive may be provided as a filmand be laminated on the bottom surface 20 of the lowest layer 14 a. Atthe time of attaching the stack 10 to the eye protector 12, theprotective liner can be removed from the dry mount adhesive layer 18 a.In operation, pressure can be applied to the stack 10 against the lens16 of the eye protector 12 to adhere stack 10 to the eye protector 12.In some embodiments, the dry mount adhesive 18 a can be pre-applied tothe bottom surface 20 of the lowest layer 14 a and then covered with aprotective liner to prevent contamination of the dry mount adhesivelayer 18 a prior to mounting of the stack 10 to the eye protector 12 ofthe helmet.

The layers 14 of the stack 10 may be oversized with respect to the eyeprotector 12. In some aspects, a user may cut the stack 10 of fit an eyeprotector 12 so that one size may fit a plurality of different eyeprotectors 12. Alternatively, the stack 10 can have an outer peripherythat has been pre-cut to fit a particular eye protector. An example ofone such configuration is shown in FIG. 2. However, other configurationsof pre-cut stacks 10 of layers 14 are also contemplated.

Referring again to FIG. 1, a stack 10 may be mounted to an eye protector12 (e.g., a face shield, eye shield, or visor) of a helmet, as shown.Although various embodiments and aspects described herein relate to aface shield of a helmet, it is also contemplated that the stack 10 maybe mounted to other types of eye protection devices such as goggles(e.g., ski goggles, snowboard goggles, motocross goggles), glasses(e.g., combat eyewear, sunglasses, prescription glasses), face shieldsfor dentistry, medical hoods, welding masks, and the like. Additionally,the stack 10 may be mounted to a video display (e.g., a televisionscreen, a computer monitor, a tablet device, a smart phone device,etc.), a touch sensitive screen, a window, or windshield. The variousembodiments and aspects described herein may be applied to otherstructures and devices.

FIG. 3 shows a cross-sectional view (cut along line 3-3 of FIG. 2) ofthe stack 10 and the lens 16 of an eye protector 12. The transparentlens 16 of the eye protector 12 can be fabricated from a polycarbonatematerial. In some embodiments, the refractive index for polycarbonatematerial can be between about 1.55 and about 1.65. More specifically,the refractive index of the polycarbonate material can be between about1.58 and 1.59. Even more specifically, the refractive index of thepolycarbonate material can be about 1.5849. The bottom surface 20 of thestack 10 (i.e., the bottom surface of the lowest removable layer 14 a ofthe stack 10) may have a dry mount adhesive layer 18 a disposed thereonfor securing the stack 10 to the top surface 22 of the lens 16. The drymount adhesive layer 18 a can be optically clear and/or transparent andcan define a refractive index. The refractive index of the dry mountadhesive layer 18 a may be about equal to the refractive index for theeye protector 12. More particularly, the refractive index for the drymount adhesive layer 18 a may be within about 0.2 of the refractiveindex for the lens 16. If the lens 16 is fabricated from a polycarbonatematerial, then the adhesive layer 18 a may be selected so that itsrefractive index is between about 1.7849 and 1.3849. In someembodiments, the selected dry mount adhesive layer 18 a will have therefractive index as described, while also having material propertiesallowing the stack 10 to be dry mounted to the lens 16 such that airbubbles can be pressed out after mounting, and while maintaining a peelstrength that allows the stack 10 to maintain a bond with the lens 16 inspite of the removal of upper layers 14 of the stack 10, and in the faceof high wind speeds.

Refraction is a change in direction in which waves travel when they passfrom one medium into another. Light waves are refracted (i.e., bent)when they pass at an angle from one medium into another because thevelocity of light is different in each of the mediums. The amount that aray of a certain wavelength bends in passing from one medium intoanother is indicated by the refractive index between the two mediums forthat wavelength. The refractive index indicates the amount that thelight ray bends as it passes out of one medium into another. When lightpasses from air into a denser material (e.g., transparent film or lens),the speed of the light decreases. When light enters the denser materialat an angle other than a right angle, this decrease in the speed oflight causes the light ray to bend at the point of entry. This bendingis referred to as refraction.

The refractive index of a medium (also referred to as the index ofrefraction) is a dimensionless number representing the ratio between thespeed of light in a vacuum and the speed of light in the medium. Thatis, the refractive index n of a substance can be written as n=c/v, wherec is the speed of light in a vacuum (about 299,792,458 meters persecond), and v is the speed of light in the substance. For example, therefractive index of water (at about 20° C.) can be about 1.33, meaningthat light travels 1.33 times slower in water than it does in vacuum.Further, the refractive index of air can be about 1.000293, meaning thatlight travels 1.000293 slower in air than it does in a vacuum. Therefractive index determines the angle at which light is bent, orrefracted, when passing from one material to another. The ratio ofrefractive indices between two mediums is also relevant to the amount oflight that is internally reflected when light passes from one medium tothe other. Thus, when combining or attaching multiple layers ofoptically clear material together, the ratio of refractive indicesbetween the two mediums will determine the amount of light that isinternally reflected between the mediums away from the eyes of thewearer. Accordingly, the greater the mismatch between two mediumsattached to one another, the less light will be able to pass through thecombined materials to the eyes of the wearer.

The dry mount adhesive layer 18 a may be disposed on the bottom surface20 of the lowest layer 14 a in a continuous uninterrupted fashion (e.g.,without perceivable breaks or gaps in the adhesive layer). In oneexample, the dry mount adhesive layer 18 a is applied to cover a viewingangle 24 through the eye protector 12, where the viewing angle 24generally defines a range of vision of the eyes 80 of the wearer. Theleft and right edges 28, 30 and the top and bottom edges 32, 34 (seeFIG. 2) of the dry mount adhesive layer 18 a may cover the viewing angle24 through the eye protector 12 when the stack 10 is mounted to the lens16. The viewing angle 24 may correspond to the outer limits of thecontinuous, uninterrupted dry mount adhesive layer 18 a which may extendto or beyond the center of gaze of the eyes 80 of the wearer of the eyeprotector 12.

Depending on the intended use of the eye protector 12, the viewing angle24 defined by the coverage of the dry mount adhesive layer 18 a mayincrease or decrease as desired. By way of example and not limitation,the continuous uninterrupted coverage of the dry mount adhesive layer 18a may be sufficiently large so that the dry mount adhesive layer 18 aextends beyond the near peripheral vision, mid peripheral vision or farperipheral vision with the stack 10 mounted to the eye protector 12. Inother words, when a wearer is wearing an eye protector 12 with a stack10 mounted thereon, the dry mount adhesive layer 18 a can be configuredto at least cover all or a portion of the center of gaze of the wearer.Optionally, the continuous uninterrupted coverage of the dry mountadhesive layer 18 a may be larger to cover the center of gaze of thewearer plus the near peripheral vision and beyond to the mid-peripheralvision and even as far as the far peripheral vision.

In some embodiments, the stack 10 may be mounted to the eye protector 12so that no perceivable air, or virtually no perceivable air, is trappedbetween the lowest layer 14 a and the lens 16 of the eye protector 12.

The stack 10 may have a plurality of transparent layers 14 a-n stackedupon each other. In one example, the layers 14 a-n may be fabricatedfrom a transparent film or lens. The film may be polyethyleneterephthalate (PET), which may a refractive index of about 1.57 to about1.67, for example.

The plurality of layers 14 a-n may be removably attachable to each otherwith an interposed adhesive layer (e.g., 18 b and 19 c). In one example,the interposed adhesive 18 b, 18 c may be the same type of adhesiveapplied to the bottom surface 20 of the lowest layer 14 a. In thisexample, the interposed adhesive 18 b may have a refractive index ofabout 1.492 if a PMMA adhesive is used or between about 1.45 to 1.54 ifa high index adhesive is used, as mentioned above. In some embodiments,the interposed adhesive 18 b may be another optically clear adhesive,provided that the refractive indices of the interposed adhesive 18 b,dry mount adhesive layer 18 a, transparent lens 16 and the layers 14 areall within 0.2 of each other. Thus, if the lens 16 is fabricated from apolycarbonate material having a refractive index of about 1.5849, andthe layers of the stack 10 are fabricated from a PET having a refractiveindex of about 1.62, then the dry mount adhesive layer 18 a may beselected so to have a refractive index is between about 1.7849 and 1.42so as not to deviate by more than 0.2 from the refractive indices of thelens 16 and the layers 14 of the stack 10, respectively. And in someembodiments, the dry mount adhesive layer 18 a will be selected to havethe refractive index as described, while also having other materialproperties described above (i.e. peel strength, self-wetting, allowingfor removal of air, etc.).

The adhesive 18 b interposed between any two layers 14 may becoextensive with the dry mount adhesive layer 18 a on the bottom surface20 of the lowest layer 14 a. In this regard, the coverage of theinterposed adhesive 18 b can be sufficiently large, continuous anduninterrupted so that the interposed adhesive 18 b covers the entirecenter of gaze of the person, or center of gaze plus the near peripheralvision, mid peripheral vision or even as far as the far peripheralvision through the eye protector 12. In some embodiments, the interposedadhesive 18 b may be disposed between the layers 14 a-n so that no air,or virtually no air, is perceivably trapped between the upper and lowerlayers 14 of the stack 10.

As shown in FIG. 2, the interposed adhesive 18 b may extend to the veryedge of the layers 14 a-n except for the lateral end portions 38. Thelateral end portions 38 of the layers 14 a-n may thus be adhesive free,thereby providing an area for a wearer to grasp and peel off theuppermost layer 14 a-n to expose a clean lower layer 14 or the lens 16of the eye protector 12.

Referring again to FIG. 3, the stack 10 may have three layers (14 a, 14b, and 14 c); however, it is contemplated that the system may have oneor more layers 14 a-n (e.g., seven layers 14). When a wearer tears offthe uppermost layer 14 c, the interposed adhesive layer 18 c can bepulled off and removed from the next lower layer 14 b. The interposedadhesive 18 c can remain with the uppermost layer 14 c that has justbeen removed. To this end, the bottom surface of the uppermost layer 14c and/or the top surface of the lower layer 14 b may be treated so thatthe interposed adhesive 18 c has a lower peel strength to the topsurface of the lower layer 14 b compared to the bottom surface of thetop layer 14 c. Additionally, the peel strength of the interposedadhesive 18 may be greater between higher pairs of layers 14 compared tothe peel strength of the interposed adhesive 18 between lower pairs oflayers 14. By way of example, the force required to peel off layer 14 bfrom layer 14 a may be greater than the force required to peel off layer14 c from layer 14 b. In this manner, peeling off the uppermost layer 14c, does not cause the layer 14 b immediately below the uppermost layer14 c to delaminate from the stack 10. The layers 14 a and 14 b,therefore, can remain with the stack 10 attached to the eye protector 12after removing or peeling off layer 14 c. Further, the peel strengthshould also be such that removal of the layer 14 or stack 10 does notleave behind residual adhesive on the surface of the lens 16. That is,the peel strength can be low enough so that the adhesive layer remainsattached to the layer that has been peeled away. Although the peelstrength between upper and lower pairs of layers 14 is contemplated asvarying, it is also contemplated that the peel strengths between upperand lower pairs of layers 14 may be equal to each other. In someembodiments, the peel strength between the layers can be about 10 gramsto 50 grams, with an average peel strength between about 25 grams andabout 30 grams, measured using a 180° test at a rate of 12 inches perminute.

To further facilitate removal of a layer 14 individually or one by one,the stack 10 can include an outer edge 42 of the adhesive layer 18 thatis progressively offset outward between each successive lower pairs oflayers 14, as shown, for example, in FIG. 5. By way of example and notlimitation, the adhesive layer 18 c between an upper pair of layers 14 cand 14 b may define an edge 42 c. The outer edge 42 b of the next loweradhesive layer 18 b may be positioned slightly outward from theimmediately upper adhesive layer 18 b. The dry mount adhesive layer 18 adisposed on the bottom surface of the lowest layer 14 a may have an edge42 a that is disposed even further outward compared to the outer edge ofthe middle adhesive layer 18 b. This outward progression facilitatesremoval of only the uppermost layer one by one. In this aspect, the peelstrength is preferably progressively stronger between lower pairs oflayers 14 but it is also contemplated that the peel strengths betweenupper and lower pairs of layers 14 are equal to each other. Thepositioning of the outer edges 42 of the adhesive layer 18 facilitatesremoval of the uppermost layer one by one, as it allows a wearer todiscern between the various layers, and readily grab and separate onelayer 14 of the stack 10 (in particular, the uppermost layer) from theothers.

Referring to FIG. 4, the stack 10 may have tabs 26 a-n that extend outfrom the opposed end portions of the transparent layers 14 a-n. FIG. 4shows the layers 14 a-n on the right side of the stack 10 being peeledslightly upward to demonstrate that tab 26 c can be used to peel off thetop layer 14 c, tab 26 b can be used to peel off the middle layer 14 b,and tab 26 a can be used to peel off the lowest layer 14 a. The tabs 26a-n may be sufficiently large for the person's index finger and thumb tograsp and pull off the uppermost layer 14 during use. The tabs 26 a-nmay be radially offset for each successive lower layer 16 to provide anintuitive tab removal system as shown in FIG. 4. Additionally and/oralternatively, the tabs 26 a-n may be linearly offset. In FIG. 4, thetabs 26 a-n are radially offset from an adjacent tab 26 of theimmediately upper or lower layer 14.

In use, a wearer can grasp the tab 26 c and peel off the uppermost layer14 c when the uppermost layer 14 is soiled or visibility through thestack 10 is reduced to an unacceptable level. When visibility throughthe stack 10 is again reduced to an unacceptable level, the wearer cangrasp tab 26 b to remove the next uppermost layer 14 b. The process canbe repeated until the last layer 14 a is removed by grasping and peelingoff the last layer 14 which is adhered to the transparent lens 16 of theeye protector 12. Thus, the stack 10 can be configured such that each ofa plurality of removable layers 14 can be removed to expose a clean andrelatively clear viewing surface.

Referring again to FIG. 5, which shows a cross section of the stack cutalong line 5-5 of FIG. 2, the layers 14 a-n of the stack 10 may beadhered to each other so that the end portions are configured in astepped manner. The layers 14 of the stack 10 may each have an outeredge 36 a-n. The outer edge 36 c of the uppermost layer 14 c may extendout further than the outer edge 36 b of the lower layer 14 b. To peeloff the uppermost layer 14 c, the wearer can grasp the outer portion oflayer 14 c by indexing his or her fingers with the outer most edge 36 c.The wearer may then pull up on the outer portion 38 of the layer 14 c toremove the uppermost layer 14 c off of layer 14 b. In some embodiments,the outer portion 38 of the layer 14 c will not have adhesive so thatthe user may grasp the outer portion 38 of layer 14 c.

The present disclosure also provides methods and processes for mountinga stack (e.g., stack 10) to an eye protector, and for protecting an eyeprotector (e.g., eye protector 12) without significantly reducing visualacuity through the eye protector. FIG. 6 is a flow diagram of an exampleprocess 110 for mounting a stack to an eye protector. At step 100, thestack can be formed, for example, by cutting the layers of the stack tofit the size of the eye protector. In some embodiments, step 100 canalso include laminating the layers of the stack together with anadhesive, for example, a high index silicone adhesive. Step 100 can alsoinclude applying a dry mount adhesive layer to a lower surface of thestack (e.g., a PMMA adhesive), and providing a protective liner over thedry mount adhesive. At step 100, the adhesive can be selected to havematerial properties sufficient to match the refractive index of theadhesive with the refractive indices of the lens and the removablelayers of the stack within about 0.2, and that demonstrates adhesiveproperties described herein with respect to peel strength, self-wetting,and/or dry mounting, for example.

After cutting the stack, a protective liner can be removed from thelowest layer of the stack to expose a dry mount adhesive (e.g., drymount adhesive layer 18 a described herein) at step 102. Removal of theprotective liner can expose the dry mount adhesive and thus prepares thestack for dry mounting to the eye protector. In some embodiments, theprotective liner can be removed prior to cutting of the stack.

With the adhesive exposed, the lowest layer of the stack can be adheredand/or attached to the lens (e.g., lens 16 as described herein) of theeye protector at step 104. In some aspects, step 104 can includemounting portions of the stack to corresponding protrusions or pins onthe eye protector to assist in the support process. However, in someembodiments, the stack can be applied directly to the lens without theuse of pins or other mounting assistance techniques.

In some embodiments, step 104 also includes removing air bubbles or airpockets between the lowest layer and the eye protector. For example, atstep 104, most, or even all of the air bubbles or air pockets can beremoved. This can be accomplished, for example, by applying a pressureto the surface of the stack and moving that pressure towards the edgesto push out the air bubbles or air pockets. For example, the air bubblescan be removed with the assistance of a finger, a squeegee, a card, oranother rigid surface that can help to press and move the air bubbles tothe edge of the stack. This can be facilitated if the dry mount adhesiveis self-wetting. For example, the dry mount adhesive can be a PMMA orother self-wetting material that maintains a bond between the stack andthe eye protector, while allowing air that forms therebetween to beremoved.

During use, visibility through the eye protector may be unacceptablyreduced through soiling or damage to the uppermost layer, for example,by splattering of fluids and debris (e.g., mud, dirt, water, etc.). Inthis manner, at step 106, the method can include removing the uppermostlayer of the stack, one-by-one, as described above. In this way, the drymount adhesive adhering the stack to the eye protector can form a peelstrength that is strong enough to maintain the attachment of the stackto the eye protector even when the uppermost layer of the stack is beingremoved.

Embodiments of the system disclosed herein have been described inrelation to a stack of three removable layers (e.g., layers 14 a, 14 b,and 14 c). However, it is also contemplated that the system 10 may havemore or fewer than three layers. For example, some embodiments of astack may have one or two layers, and other embodiments may have four,five, six, seven, or more layers, as desired.

The thickness of the layers of the stack and/or adhesive can also varydepending on the intended use. For example, in some embodiments, each ofthe layers of the stack may have a thickness of between about 0.0005inches (i.e., half a mil) to about 0.014 inches (i.e., 14 mils). In someembodiments, depending on the intended use, the number of layers used,and other considerations, the layers may have a greater or smallerthickness. Further, in some embodiments, the thickness of each of theremovable layers of the stack can all be the same; however, someembodiments may include layers that vary in thickness from layer tolayer. For example, some layers of the stack can be about 0.008 inches(8 mils) thick, while other layers of the stack can be about 0.002 (2mils) inches thick. In some embodiments, the thickness of the layers ofadhesive may be negligible. By way of example and not limitation, ifthree (3) 0.001 inch (1 mil) thick layers are stacked upon and adheredto each other, the adhesive layers may be of negligible thickness sothat the stack of three layers would still measure about 0.003 inchesthick. In some embodiments, the thickness of the adhesive layers can beabout 0.00059 inches (i.e., about 0.59 mils, or about 15 microns) thick.

The system disclosed herein has been described in relation to adhering astack of removable layers to a face shield of a helmet. However, it isalso contemplated that the stack can be adhered, for example, to othereye protectors, such as an eye shield of a goggle. In such an example,the eye shield of the goggle may be fabricated from a flexible filmlayer configured to inhibit, limit, or prevent snow and/or dirt fromirritating the user's eyes when skiing during a snowfall, or riding amotocross motorcycle through dirt and/or mud. In this manner, therefractive indices of the removable layers and the adhesive layers ofthe stack can be matched to the flexible film layer of the goggle sothat the refractive indices of the removable layers of the stack, theadhesive layers of the stack, and the flexible film layer of the goggleare all matched within 0.2 of each other.

In some embodiments, stacks can be configured for dry mounting to lensesor shields that already have pins installed thereon. For example, thestack can be provided with holes configured to align with the pinsmounted in such lens or shield, while also including the dry mountadhesive layer on the lower surface of the stack. In this manner,consumers will not need to dispose of older eye protectors, faceshields, helmets, etc., in order to use the stacks of the presentdisclosure. Additionally and/or alternatively, stacks can bemanufactured in a shape and configuration designed to not interfere withany existing pins or other objects on a lens or shield. In this manner,the stacks can be configured to be used on eye protectors of varyingshapes, sizes and configurations, regardless of whether the eyeprotector is equipped to handle pin mounts.

The above description is given by way of example, and not limitation.Given the above disclosure, one skilled in the art could devisevariations that are within the scope and spirit of the inventiondisclosed herein, including various ways of applying the adhesive to thelayers. Further, the various features of the embodiments disclosedherein can be used alone, or in varying combinations with each other andare not intended to be limited to the specific combination describedherein. Thus, the scope of the claims is not to be limited by theillustrated embodiments. All references cited in the present disclosureare hereby incorporated by reference in their entirety.

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 21. A method of protecting an eye protector, the eyeprotector having a center portion defining a center of gaze of a wearer,the eye protector also having, a lens configured to protect the wearerfrom projectiles, the lens having a continuous surface without holes orpins, the method comprising: selecting an optically clear lens stackhaving a plurality of lens layers laminated to one another with aremovable adhesive layer, each removable lens layer and removableadhesive layer having a refractive index matched to within about 0.2 ofone another; removing a protective liner from a bottom surface of theoptically clear lens stack to expose an optically clear dry mountadhesive layer on the lens stack, the optically clear dry mount adhesivelayer forming an outer periphery configured to correspond with thecenter portion of the eye protector, and dry mounting the opticallyclear lens stack to the lens via the other periphery of the dry mountadhesive layer, wherein the dry mounting comprises positioning theoptically clear lens stack so that it covers the center of gaze definedby the center portion of the eye protector, wherein the dry mountingestablishes a dry mounting adhesive peel strength between the opticallyclear stack and the lens that is greater than a peel strength betweeneach removable layer of the optically clear lens stack, wherein theouter periphery of the dry mount adhesive layer is configured to form aphysical barrier that prevents debris from accumulating between alowermost layer of the optically clear lens stack and the lens, andwherein the dry mounting is performed without applying tension to thestack.
 22. The method of claim 1, wherein the dry mount adhesive layerforms a continuous and uninterrupted adhesive layer over at least thecenter portion of the eye protector.
 23. The method of claim 2, whereinthe dry mounting adhesive layer is self-wetting and has a dry mountadhesive layer refractive index matched to within about 0.2 of therefractive index of each removable lens layer and removable adhesivelayer.
 24. The method of claim 3, further comprising the step ofbreaking an adhesive bond between the stack and an uppermost removablelayer of the stack to remove the uppermost removable layer, the breakingstep further comprising gripping and pulling a tab on the uppermostlayer of the stack to remove the uppermost layer and expose a lowerlayer of the stack.